Terminal device and wireless communication system

ABSTRACT

A terminal device is capable of communicating with a master wireless device. The terminal device includes a control circuit. The control circuit has operating modes including a normal mode for outputting startup information relating to startup of the terminal device, and a registration mode for outputting registration information relating to registration with the master wireless device. One of the operating mode of the control circuit shifts to the registration mode based on timing of plural startups of the terminal device. The terminal device can shift to the registration mode using the same operation and mechanism as operating in the normal mode.

TECHNICAL FIELD

The present invention relates to a terminal device and a wirelesscommunication system.

BACKGROUND ART

A wireless communication system includes a master wireless device and aterminal device capable of communicating with the master wirelessdevice. Some examples of such wireless communication systems will bedescribed below.

A wireless communication system is adapted to collect biomedicalinformation, such as pulses of a subject under the examination. In thiswireless communication system, a terminal device is attached to thesubject, and collects biomedical information of the subject. Theterminal device then transmits the biomedical information to a masterwireless device via wireless communications.

Another wireless communication system is used by a manager of a buildingto collect power consumption information from load circuits in adistribution panel. A terminal device is disposed inside thedistribution panel, and collects an amount of the electric powersupplied to each of the load circuits as the power consumptioninformation. The terminal device transmits the power consumptioninformation to a master wireless device via wireless communications.

In these wireless communication systems, the terminal device is pairedwith the master wireless device when initialized so as to ensure thatthe terminal device does not transmit the information to an unrelatedmaster wireless device. This pairing is called as registrationhereinafter. Once the registration is completed, communications of theinformation are established between the terminal device and the masterwireless device.

Some conventional systems similar to the above wireless communicationsystems are disclosed in the patent literatures listed below.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laid-Open Publication, No. 2004-096429

PTL 2: Japanese Patent Laid-Open Publication, No. 2009-105667

SUMMARY

A terminal device is capable of communicating with a master wirelessdevice. The terminal device includes a control circuit. The controlcircuit has operating modes: a normal mode for outputting startupinformation relating to startup of the terminal device; and aregistration mode for outputting registration information relating toregistration of the terminal device with the master wireless device. Thecontrol circuit shifts one of the operating modes to the registrationmode based on timing of plural startups of the terminal device.

A wireless communication system includes a master wireless device and aterminal device capable of communicating with the master wirelessdevice. The terminal device includes a control circuit. The controlcircuit has operating modes: a normal mode for outputting startupinformation relating to startup of the terminal device; and aregistration mode for outputting registration information relating toregistration of the terminal device with the master wireless device. Thecontrol circuit shifts one of the operating modes to the registrationmode based on timing of plural startups of the terminal device. Theregistration information is transmitted to the master wireless devicefrom the terminal device, and received by the master wireless device,thereby registering the terminal device with the master wireless device.

The terminal device can shift the operation mode to the registrationmode using the same operation and mechanism as the normal mode.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a wireless communication system accordingto Exemplary Embodiment 1 for illustrating an overall configurationthereof.

FIG. 2 is a block diagram of a terminal device according to Embodiment 1for illustrating an electrical configuration thereof.

FIG. 3 is a block diagram of a master wireless device according toEmbodiment 1 for illustrating an electrical configuration thereof.

FIG. 4 is a sequence diagram of the wireless communication systemaccording to Embodiment 1 for illustrating a registration methodthereof.

FIG. 5 is a timing chart of an operation of a control circuit of theterminal device according to Embodiment 1 shifting to a registrationmode.

FIG. 6 is a block diagram of a terminal device according to ExemplaryEmbodiment 2 for illustrating an electrical configuration thereof.

FIG. 7 is a block diagram of a master wireless device according toEmbodiment 2 for illustrating an electrical configuration thereof.

FIG. 8 is a sequence diagram of a wireless communication systemaccording to Embodiment 2 for illustrating a registration methodthereof.

FIG. 9 is a block diagram of a terminal device according to ExemplaryEmbodiment 3 for illustrating an electrical configuration thereof.

FIG. 10 is a block diagram of another terminal device according toEmbodiment 3 for illustrating an electrical configuration thereof.

FIG. 11 is a timing chart of an operation of a control circuit of theterminal device according to Embodiment 3 shifting to a registrationmode.

DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention will be described belowwith referring to the accompanying drawings. The following embodimentsare examples of the present invention, and do not be construed aslimiting the scope of the present invention.

1. Exemplary Embodiment 1 1-1. General Outline

FIG. 1 schematically illustrates an overall configuration of a wirelesscommunication system according to Exemplary Embodiment 1. This wirelesscommunication system is used for detecting opening and closing of awindow to check whether or not the window is carelessly left open, or tocheck presence or absence of an intruder through the window. Thiswireless communication system is an energy-harvesting wireless systemfeaturing extremely low-power consumption.

The wireless communication system according to Embodiment 1 includesmaster wireless device 300 and terminal device 100. Terminal device 100is mounted inside window frame 50. Master wireless device 300 is locatedaway from terminal device 100. User 51 of this wireless communicationsystem is, for instance, a construction worker of the window or aresident of the house. An operation by user 51 to open or close window52 causes terminal device 100 to generate electricity, and to informmaster wireless device 300 of the opening or closing of window 52.Terminal device 100 is registered or paired with that master wirelessdevice 300 when they are initialized. Once the registration iscompleted, master wireless device 300 and terminal device 100 hold aregistered relationship. This allows communications of information to beestablished between the devices. In the case that plural windows aremonitored as objects, the same number of terminal devices 100 as thewindows may be prepared and mounted to the windows. Master wirelessdevice 300 establishes registered relationship with each of terminaldevices 100.

A registration method which is different from that of Embodiment 1 for acomparison with Embodiment 1 will be described below. In this method, aterminal device includes a switch for shifting an operating mode of theterminal device to a registration mode. When the user turns on theswitch, the terminal device transmits registration information, such asan identifier, of the terminal device and an encryption key to a masterwireless device. The registration is completed when the master wirelessdevice receives and stores the registration information.

Another registration method will be described below. In this method, theuser starts a terminal device in a normal operating mode by opening andclosing a window. This causes the terminal device to transmit startupinformation, such as an identifier, of the terminal device and encrypteddata relating to the opening and closing of the window to a masterwireless device.

The master wireless device inquires a database of a server of anencryption key of the terminal device based on the identifier. Theregistration is completed when the master wireless device stores theencryption key obtained from the database.

In the former registration method, the user needs to push the switch ofthe terminal device. This method therefore prevents the terminal devicefrom being installed inside a building fixture, such as a window frame.The terminal device may have a large size in order to provide theterminal device with a mechanism that is different from the mechanismused in the normal mode. Moreover, in the latter registration method,the master wireless device is required to inquire the database ofregistration information. Therefore, the wireless communication systemcannot self-conclude the registration tasks. In addition, it may taketime to inquire the database. Furthermore, considerable efforts maybecome necessary to configure the system, and to manage and control thedata.

In the wireless communication system according to Embodiment 1, incontrast to these registration methods, user 51 opens and closes window52 plural times according to predetermined timings. When terminal device100 determines that these timings coincide with the predeterminedtimings, terminal device 100 shifts the operating mode to a registrationmode. In the registration mode, terminal device 100 communicates withmaster wireless device 300 about the registration.

As described, terminal device 100 according to Embodiment 1 can shift tothe registration mode in response to opening and closing of window 52.In other words, terminal device 100 is capable of shifting to theregistration mode using the same operation and mechanism as it operatesin the normal mode. In addition, master wireless device 300 is notrequired to inquire the database of the registration information.

1-2. Electrical Configuration 1-2-1. Electrical Configuration ofTerminal Device

An electrical configuration of terminal device 100 according toEmbodiment 1 will be described with reference to FIG. 2. FIG. 2 is ablock diagram of terminal device 100 for illustrating the electricalconfiguration. Terminal device 100 includes power generator circuit 10,voltage converter 11, control circuit 12, determinator circuit 13,transmitter circuit 14, and antenna 15.

Power generator circuit 10 generates electricity by using energyproduced by opening and closing of window 52. Electric power Vbatobtained from power generator circuit 10 is supplied to control circuit12 and transmitter circuit 14 of terminal device 100. The electric powerVbat has a voltage ranging from about 0V to about 10V. The electricpower Vbat is rectified by diode D11, stored once in capacitor C11 forcharging the electricity, and input to voltage converter 11.

Voltage converter 11 converts the voltage of electric power Vbat.Voltage converter 11 has an under-voltage lockout (UVLO) function toprevent malfunctions. According to Embodiment 1, an UVLO voltage as athreshold is 1.85V. Any voltage higher than 1.85V is converted to 1.8Vby voltage converter 11, and supplied to control circuit 12 aspower-supply voltage VDD. A waveform of power-supply voltage VDD becomesa pulse shape since the electric power Vbat is generated by powergenerator circuit 10 each time window 52 is opened or closed.

Control circuit 12 outputs a variety of signals in response topower-supply voltage VDD input thereto. Operating modes: a normal modeand a registration mode are set to control circuit 12. When power-supplyvoltage VDD is input to control circuit 12 in the normal mode, controlcircuit 12 outputs startup information, such as an identifier ofterminal device 100, relating to startup of terminal device 100 and datarelating to opening and closing of window 52. The data relating toopening and closing of window 52 is encrypted for security. Theencrypted data is hereafter referred to as encrypted data. On the otherhand, when power-supply voltage VDD is input to control circuit 12 inthe registration mode, control circuit 12 outputs registrationinformation, such as the identifier of terminal device 100, relating toregistration of terminal device 100 with master wireless device 300 andan encryption key to decrypt the encrypted data. Control circuit 12includes non-volatile memory 121, and central processing unit (CPU) 122.The identifier and the encryption key are stored in non-volatile memory121. Central processing unit 122 performs various functions, such asnumerical calculation, information processing, and control of circuits.

Determinator circuit 13 determines whether or not a predetermined timeelapses from a preceding startup of terminal device 100 to a nextstartup of terminal device 100, and is used to determine whether or notthe operating mode of control circuit 12 is shifted from the normal modeto the registration mode. Determinator circuit 13 is a time constantcircuit that includes diode D21, resistor R21, and capacitor C21. Thecapacitance of capacitor C21 is 1 μF, and the resistance of resistor R21is 1 MΩ according to Embodiment 1. Time constant τ of determinatorcircuit 13 is 1 second. A voltage input to determinator circuit 13 froman output port of control circuit 12 decreases according to the timeconstant τ. An output voltage that decreases in determinator circuit 13can be detected at an input port of control circuit 12. A time intervalfrom the preceding startup of terminal device 100 to the next startup ofterminal device 100, that is, the interval from the last opening orclosing of window 52 to the next opening or closing of window 52 by user51 can be detected based on output values of determinator circuit 13.The operation in which control circuit 12 shifts from the normal mode tothe registration mode based on the outputs of determinator circuit 13will be detailed later an item of registration method.

Transmitter circuit 14 transmits signals output from control circuit 12to master wireless device 300 via antenna 15. Transmitter circuit 14transmits the signals containing, e.g. the startup information and theregistration information by using the electric power obtained fromgenerator circuit 10.

1-2-2. Electrical Configuration of Master Wireless Device

An electrical configuration of master wireless device 300 according toEmbodiment 1 will be described with referring to FIG. 3. Master wirelessdevice 300 includes receiver circuit 30, antenna 31, control circuit 32,and power supply 33. Control circuit 32 includes non-volatile memory321, and central processing unit 322.

Receiver circuit 30 receives signals transmitted from terminal device100 via antenna 31.

Control circuit 32 performs tasks, such as the decrypting of theencrypted data received by receiver circuit 30 and the registration ofterminal device 100 by using central processing unit 322. Non-volatilememory 321 stores the identifier and the encryption key of terminaldevice 100.

Power supply 33 supplies electric power to receiver circuit 30, controlcircuit 32, and the like components. Power supply 33 is connected withan external power source.

1-3. Registration Method

Referring to FIG. 4 and FIG. 5, the registration method of terminaldevice 100 and master wireless device 300 will be described below. FIG.4 is a sequence diagram showing the registration method while FIG. 5 isa timing chart when operation of control circuit 12 of terminal device100 shifts to the registration mode. Both operators A and B shown inFIG. 4 are construction workers of the window where terminal device 100and master wireless devices 300 are installed. The operator A may bedifferent from the operator B, or may be identical to the operator B.

Terminal device 100 operates intermittently, as shown in FIG. 4.According to Embodiment 1, electricity is generated by terminal device100 in itself only when window 52 is opened or closed. This electricpower is supplied to terminal device 100. Terminal device 100 starts upsimultaneously to the supplying of the electric power and operates onlyfor a predetermined time after the startup, that is, for thepredetermined time after the opening or closing of window 52. Terminaldevice 100 then stops after operating for the predetermined time as theelectric power is used up completely (S101).

On the other hand, master wireless device 300 continuously operates anytime since master wireless device 300 is connected to the externalsupply source. An operating mode of master wireless device 300 undernormal conditions is a normal mode for receiving startup informationfrom terminal device 100 (S301). When the operator B operates masterwireless device 300 and provides a command of shifting to a registrationmode, master wireless device 300 starts a registration process (S302).

While terminal device 100 stops (S101), the operator A opens or closeswindow 52. This causes terminal device 100 to generate electricity, andto start up, i.e., wake up (S102). Upon starting up, terminal device 100determines whether or not timing of the startup coincides with apredetermined timing pattern for shifting to the registration mode. Ifit is not determined that the timing of the startup coincides with thepredetermined timing pattern (S103), the operating mode is shifted tothe normal mode (S104). In addition, terminal device 100 storesinformation of the startup timing in non-volatile memory 121. Afterthat, terminal device 100 transmits startup information including anidentifier of terminal device 100 and encrypted data relating to theopening or closing of window 52 to master wireless device 300. Accordingto Embodiment 1, the identifier and the encrypted data are transmittedrepetitively plural timed per each startup in order to improvereliability of the transmission. However, the transmission may transmitthem only once per each startup. When the transmission is completed andthe electric power is used up completely, terminal device 100 stopsagain (S105).

When operator A intends to shift the operating mode of control circuit12 of terminal device 100 from the normal mode to the registration mode,the operator A opens and closes window 52 plural times at apredetermined timing pattern. According to Embodiment 1, window 52 isopened and closed five times such that window 52 is opened, closed,opened, closed, and again opened, for example. At this moment, a timeinterval between the second and the third opening-and-closing operationis not shorter than t2 (seconds) whereas other time intervals areshorter than t1 (seconds). Then, terminal device 100 starts up accordingto a timing pattern corresponding to the timing pattern of opening andclosing of window 52 five times. Terminal device 100 starts up everytime window 52 is opened or closed, and repeats a combination of stepsS102 to S105 (S106) described above (S107). In addition, information ofthe individual startup timings is stored in non-volatile memory 121.

According to Embodiment 1, the step S102 corresponds to the firststartup, the step S107 corresponds to processes involving the second tofourth startups, and the step S108 corresponds to the fifth startup.

Upon determining in step S109 that the timing pattern of the fivestartups stored in non-volatile memory 121 coincide with a predeterminedtiming pattern, control circuit 12 of terminal device 100 shifts to theregistration mode (S110). This determination of the timing patterns willbe described later with referring to FIG. 5.

In the registration mode, terminal device 100 outputs registrationinformation relating to registration with master wireless device 300,that is, the identifier and the encryption key, and transmits theidentifier and the encryption key to master wireless device 300. Uponcompleting transmitting the identifier and the encryption key, terminaldevice 100 resets the timing patterns stored in non-volatile memory 121.Terminal device 100 then stops again (S112).

On the other hand, when master wireless device 300 receives theidentifier and the encryption key, i.e., the registration information,from terminal device 100 while having started the registration process,master wireless device 300 stores the identifier and the encryption keyin non-volatile memory 321 of master wireless device 300. This is tocomplete the registration with master wireless device 300 (S304).

Finally, the operator A confirms that the registration has been madecorrectly. The operator A open or closes operation of window 52 justonce to start up terminal device 100 again (S113). Terminal device 100determines a timing pattern of the startup. Terminal device 100determines that the timing pattern of the startup does not coincide withthe predetermined timing pattern (S114), terminal device 100 shifts tothe normal mode (S115). Terminal device 100 then transmits startupinformation, that is, the identifier and the encrypted data to masterwireless device 300, and then, stops (S116).

Master wireless device 300 receives the identifier and the encrypteddata from terminal device 100. When master wireless device 300 cancorrectly decrypt the received encrypted data, the registration ofterminal device 100 with master wireless device 300 is completed (S305).Master wireless device 300, upon completion of the registration, outputsregistration completion notification to the operator B, and returns tothe normal mode (S306). The registration completion notification is tonotify the operator B of the completion of the registration. Theregistration completion notification can be a signal, such as a soundand light, or may be a message, such as a mail, transmitted to apredesignated address.

The registration of the wireless communication system is executed bycommunications established between terminal device 100 and masterwireless device 300. Once the registration is completed between terminaldevice 100 and master wireless device 300, terminal device 100 andmaster wireless device 300 can communicate with each other. In otherwords, terminal device 100 transmits the startup information thereof tomaster wireless device 300 every time user 51 opens or closes window 52,so that master wireless device 300 can receive and decrypt the startupinformation. Thus user 51 can obtain information about opening andclosing of window 52 through the notification from master wirelessdevice 300 or by accessing master wireless device 300.

A method for determining whether a timing of opening and closing window52 coincides with the predetermined timing will be detailed below withreferring to FIG. 5.

FIG. 5 is a timing chart of control circuit 12 when operator A opens andcloses windows 52 five times as described above. The time intervalbetween the second and the third opening-and-closing actions is notshorter than time t2 (seconds) while other time intervals are shorterthan time t1 (seconds), as described above.

Control circuit 12 receives a pulse voltage of power-supply voltage VDDevery time window 52 is opened or closed. The pulse voltagecorresponding to power-supply voltage VDD is supplied to determinatorcircuit 13 through the output port. An output voltage from determinatorcircuit 13 is input to the input port of control circuit 12. The voltageinput to the input port decreases according to the above-stated timeconstant τ of determinator circuit 13. When a waveform of power-supplyvoltage VDD rises, control circuit 12 compares the voltage at the inputport with predetermined reference values. The reference values arepreviously determined as two values of high (H) and low (L). Bycomparing the voltage at the input port with the two reference values,control circuit 12 can obtain a time interval from the preceding startupto the next startup of terminal device 100. According to Embodiment 1,control circuit 12 determines that the time interval from the precedingstartup to the next startup is shorter than time t1 (seconds) when avoltage read at the input port is higher than the reference value (H),and outputs digit “1”. When the voltage reading at the input port islower than the reference value (L), on the other hand, control circuit12 determines that the time interval from the preceding startup to thenext startup is not shorter than time t2 (seconds), and outputs digit“0”. Therefore, control circuit 12 outputs digits of “0”, “1”, “0”, “1”and “1” in the instance of the startup timings according to Embodiment1.

Control circuit 12 compares this output pattern with the output patternpreviously stored in non-volatile memory 121, and shifts the operatingmode to the registration mode when the output patterns coincide witheach other. If the output patterns do not coincide with each other,control circuit 12 keeps the operating mode to remain in the normalmode. Control circuit 12 of terminal device 100 shifts from the normalmode to the registration mode as described above based on the timings ofthe plural startups of terminal device 100.

1-4. Beneficial Effects

According to Embodiment 1, the operating mode can be shifted to theregistration mode by the operation of opening and closing window 52similarly to terminal device 100 in the normal mode. Therefore, terminaldevice 100 does not require a mechanism, such as a switch, for switchingthe operating mode to shift to the registration mode. In addition, it isnot necessary for the user to push any switch to shift to theregistration mode. Therefore, the user can easily shift terminal device100 to the registration mode even in a case of energy-harvestingwireless device that is often built inside a building fixture ordisposed in an area not easily accessible to the user. Moreover, masterwireless device 300 is not required to inquire the database of theregistration information. The wireless communication system cantherefore complete the registration operation. In addition, the wirelesscommunication system can reduce the time required to register since itis not necessary to inquire the database. Moreover, the system itselfcan be simplified. This can hence reduce the work necessary forconstruction of the system, control and management of the data.

Although terminal device 100 of the first embodiment is suitable forsuch terminal device 100 that is equipped with power generator circuit10, it is also applicable to terminal device 100 not equipped with powergenerator circuit 10 but with a battery.

According to Embodiment 1, the expression of “opening and closing” ofwindow 52 means at least one of “opening” and “closing” of windows 52,but it may also mean “opening and closing”.

Moreover, according to Embodiment 1, “plural” in the expression of“timings of plural startups” indicates five times, it can be any numberof times without limiting it to five times. However, it is preferablythree or more times so as to reduce a malfunction.

Furthermore, according to Embodiment 1, the normal mode and theregistration mode are shown as the operating modes of control circuit12, but may be altered to be settable to other operating modes. Forexample, it may be changed to become settable to a rest mode in which nosignal is output even when terminal device 100 starts up. Terminaldevice 100 is configured to shift directly from the normal mode to theregistration mode in the step S110 shown in FIG. 4, but may be alteredsuch that it once goes into another operating mode, such as a rest mode,and then, shifts from the rest mode to the registration mode when itdetermines that the startup pattern coincides in the step S109.

According to Embodiment 1, terminal device 100 is started once again inthe step S113 after the registration of the step S304 for confirmationof the registration, but this process may be omitted. That is, theprocess of registration can be completed after the registration stepS304 without the confirming of the registration.

Moreover, according to Embodiment 1, terminal device 100 is mountedinside window frame 50. However, the location of installation is notrestricted by this embodiment. Terminal device 100 can be installed inany other place, such as a surface of window frame 50 and inside of aglass window.

According to Embodiment 1, the wireless communication system is used fordetecting opening and closing of window 52, it can also be used forother applications. Such other applications include detection of whetheror not a light, an air conditioner, or an electrical appliance isoperated, a door is opened and closed, and a window or a door is locked,as a few examples. Terminal device 100 can be disposed in a switch, adoor, a key lever, or a doorknob according to any particular applicationof the wireless communication system. Terminal device 100 is onlyrequired to generate electricity in response to on-and-off shifting ofthe switch, opening and closing of the door, and the rotation ordisplacement of the lever or the doorknob, and to start up. Moreover,this wireless communication system can be used to collect biomedicalinformation, such as pulses and blinks of an eye, of a human or ananimal In this case, terminal device 100 is disposed on a body adjacentto a blood vessel or an eyelid of the human or the animal Terminaldevice 100 hence generates electricity, and starts up according tomovement of the living body.

2. Exemplary Embodiment 2

A wireless communication system according to Exemplary Embodiment 2 willbe described with referring to FIGS. 6 to 8. The operation of terminaldevice 110 until the shifting to a registration mode is identical toboth wireless communication systems according to Embodiment 1 andEmbodiment 2. But, a registration method between terminal device 110 andmaster wireless device 310 is different after shifting of terminaldevice 110 to the registration mode. To simplify the descriptioncomponents common to both Embodiment 2 and Embodiment 1 are denoted bythe same reference numerals.

2-1. Electrical Configuration 2-1-1. Electrical Configuration ofTerminal Device

FIG. 6 shows an electrical configuration of terminal device 110according to Embodiment 2. Terminal device 110 in ludes receiver circuit16. Similar to terminal device 100 according to Embodiment 1, terminaldevice 110 includes power generator circuit 10, voltage converter 11,control circuit 12, determinator circuit 13, transmitter circuit 14, andantenna 15.

Receiver circuit 16 receives a signal from master wireless device 310through antenna 15. According to Embodiment 2, the signal from masterwireless device 310 refers to an identifier and an encryption key ofterminal device 110.

2-1-2. Electrical Configuration of Master Wireless Device

FIG. 7 shows an electrical configuration of master wireless device 310according to Embodiment 2. Master wireless device 310 includestransmitter circuit 34. Master wireless device 310 further includesreceiver circuit 30, antenna 31, control circuit 32, and power supply33, similar to master wireless device 300 according to Embodiment 1.

Transmitter circuit 34 transmits a signal to terminal device 110 throughantenna 31.

2-2. Registration Method

FIG. 8 is a sequence diagram showing the registration method of thewireless communication system according to Embodiment 2.

Terminal device 110 shifts to the registration mode in step S110similarly to Embodiment 1. According to Embodiment 2, terminal device110, upon shifting to the registration mode, and transmits an identifierof terminal device 110 and a registration request signal to masterwireless device 310 as registration information. The registrationrequest signal is a signal for requesting master wireless device 310 totransmit an encryption key. The encryption key is used to encrypt datarelating to opening and closing of a window. According to Embodiment 2,the encryption key transmitted from master wireless device 310 ischanged every time the registration is made.

When master wireless device 310, in a state of being ready forregistration (S302), receives a registration request signal fromterminal device 110, master wireless device 310 transmits to terminaldevice 110 the identifier and the encryption key of terminal device 110(S303).

Terminal device 110 stores the encryption key transmitted from masterwireless device 310 in non-volatile memory 121 (S111). If anotherencryption key is transmitted from master wireless device 310 and storedpreviously, it is replaced with the new encryption key. The registrationwith terminal device 110 is completed when the new encryption key isstored in non-volatile memory 121. Terminal device 110 then resetsprevious timing pattern stored in non-volatile memory 121, and stopsagain (S112).

Finally, operator A confirms whether or not the registration iscorrectly made, similarly to Embodiment 1. When the operator A opens orcloses window 52 just once, terminal device 110 starts up (S113).Terminal device 110 determines a timing pattern of the startup. Whenterminal device 110 determines that the timing pattern does not coincidewith a predetermined timing pattern (S114), terminal device 110 shiftsthe operating mode to a normal mode (S115). In the normal mode, terminaldevice 110 transmits startup information, that is, the identifier and anencrypted data to master wireless device 310. This encrypted data isencrypted by a new encryption key stored in the step S111. Masterwireless device 310 receives the startup information, and decrypts thereceived encrypted data by the above-stated new encryption key. Whenmaster wireless device 310 can decrypt the encrypted data correctly, theregistration of terminal device 110 with master wireless device 310 iscompleted (S305). Master wireless device 310 then sends a registrationcompletion notification to the operator B, and goes back to the normalmode (S306).

Once the registration is completed between terminal device 110 andmaster wireless device 310, terminal device 110 transmits data encryptedby the above-stated new encryption key to master wireless device 310together with an identifier of terminal device 110 when user 51 opens orcloses window 52 again. Master wireless device 310 then decrypts theencrypted data by using the encryption key, so that it can notify user51 of the information.

2-3. Beneficial Effects

According to Embodiment 2, the encryption key can be updated each timethe encryption key is transmitted from master wireless device 310.Therefore, the level of security can be improved substantially. It ishence useful for such applications that a resident of the room ischanged, and only master wireless device 310 is replaced with a newmodel, for example.

In the case where terminal device 110 can ensure generation ofsufficient power, it can be adapted to use a generally known public keycryptosystem. In this case, master wireless device 310 transmits apublic key as an encryption key in the step S303. Terminal device 110stores the public key in the step S111, and transmits data encrypted bythe public key as startup information to master wireless device 310 inthe step S115. Master wireless device 310, on the other hand, decryptsthe encrypted data by using a private key that is stored only innon-volatile memory 321 of master wireless device 310. The use of thispublic key cryptosystem can further decrease the possibility that theencrypted data is read by third parties.

According to Embodiment 2, master wireless device 310 transmits adifferent encryption key at each time to terminal device 110, but mayinstead transmit any encryption key selected at random from pluralencryption keys, for instance. Or, the same encryption key may be usedseveral times before changing it to another one, instead of changing theencryption key every time. The encryption key transmitted from masterwireless device 310 to terminal device 110 is new and different from theprevious encryption key transmitted from master wireless device 310before this key is transmitted, and for this reason the security can betightened. It is nevertheless possible to make registration even if thesame encryption key is used at all times.

Furthermore, master wireless device 310 sets the encryption keyautomatically according to Embodiment 2, but may be altered so that theoperator B chooses a desired key.

Moreover, confirmation of the registration is made before completion ofthe registration in the step S305, but this process may also be omittedaccording to Embodiment 2.

According to Embodiment 2, similarly to Embodiment 1, the operating modeof terminal device 110 can be shifted to the registration mode by theoperation of opening and closing window 52 similar to operations in thenormal mode. In addition, it is not necessary for master wireless device310 to inquire the database.

2-4. Modification

Transmission power of terminal device 110 to transmit registrationinformation to master wireless device 310 may be equal to transmissionpower of master wireless device 310 to transmit the encryption key toterminal device 110. However, the transmission power of master wirelessdevice 310 to transmit the encryption key can be larger than thetransmission power of terminal device 110 to transmit the registrationinformation. Here, master wireless device 310 has an enough amount ofusable electric power since it is connected to an external supplysource. It is therefore easier to increase the transmission power ofmaster wireless device 310 than to increase the transmission power ofterminal device 110. Terminal device 110 can receive a signal frommaster wireless device 310 more reliably by increasing the transmissionpower of master wireless device 310 to transmit the encryption key evenwhen an antenna gain of terminal device 110 is smaller than an antennagain of master wireless device 310.

In addition, a communication frequency used by terminal device 110 totransmit the registration information to master wireless device 310 maybe different from a communication frequency used by master wirelessdevice 310 to transmit the encryption key to terminal device 110. Anexample in which the wireless communication system is used in Japan willbe described below. Terminal device 110 is adapted to use a frequencyband between 928.15 MHz and 929.65 MHz, in which a maximum power allowedby the law is relatively smaller as 1 mW, for transmitting theregistration information. On the other hand, master wireless device 310is adapted to use another frequency band between 923.6 MHz and 928.0MHz, in which the allowable maximum power is relatively larger as 20 mW,for transmitting the encryption key to terminal device 110. As a result,master wireless device 310 can execute the transmission with a largepower.

Description of configurations similar to those of the first embodimentand their effects is skipped.

3. Exemplary Embodiment 3

A wireless communication system according to Exemplary Embodiment 3 willbe described below with referring to FIG. 9 to FIG. 11. Terminal device120 according to Embodiment 3 has an electrical configuration differentin part from that of Embodiment 1. In terminal device 120 according toEmbodiment 3, electric power having a voltage below the UVLO voltagethat has been wasted in the first embodiment is supplied to determinatorcircuit 13. An electrical configuration of master wireless device 300according to Embodiment 3 is identical to that of Embodiment 1. Tosimplify the description, components that are common to both Embodiment3 and Embodiment 1 are denoted by the same reference numerals.

3-1. Electrical Configuration of Terminal Device

FIG. 9 shows an electrical configuration of terminal device 120 of thethird embodiment. Terminal device 120 includes voltage detector 17, andtransistor Tr11 functioning as a switch. Similar to terminal device 100according to Embodiment 1, terminal device 120 also includes powergenerator circuit 10, voltage converter 11, control circuit 12,determinator circuit 13, transmitter circuit 14, and antenna 15.

Voltage detector 17 has an output impedance changing when a voltagebecomes not higher than a predetermined value. According to Embodiment3, the impedance becomes high at voltages exceeding the UVLO voltage,i.e., voltages higher than 1.85V, and the impedance becomes low atvoltages equal to or below the UVLO voltage.

The switch according to Embodiment 3 is implemented by transistor Tr11of FIG. 10. Transistor Tr11 is used to supply electric charge of anyvoltage not higher than the UVLO voltage to determinator circuit 13. Thebase of transistor Tr11 is connected with an output side of voltagedetector 17. Transistor Tr11 is turned on when the output impedance ofvoltage detector 17 changes to a low impedance. On the other hand,transistor Tr11 is turned off when the output impedance of voltagedetector 17 changes to a high impedance. Transistor Tr11 is providedbetween capacitor C11 storing the electric power obtained from powergenerator circuit 10 and capacitor C21 that constitutes determinatorcircuit 13. Resistor R31 is provided as a bias resistor of transistorTr11 between an input side of voltage converter 11 and the base oftransistor Tr11. This configuration can stabilize the base voltage oftransistor Tr11. By having voltage detector 17 change the outputimpedance between the low impedance and the high impedance, the voltagecan be supplied to transistor Tr11 such that transistor Tr11 is operatedas a switch to turn on and off.

According to Embodiment 3, delay line 18 is disposed between capacitorC11 and transistor Tr11. Delay line 18 is implemented by any of aresistor, a coil, a semiconductor device, and the like components.Transistor Tr11 may be turned on and electric charge is supplied tocapacitor C21 of determinator circuit 13 immediately after generation ofelectricity due to a slight delay for voltage detector 17 to detect avoltage. To cope with such situations, delay line 18 according toEmbodiment 1 can prevent the electric charge from being supplied todeterminator circuit 13 immediately after generation of the electricity.FIG. 10 shows another electrical configuration of terminal device 130according to Embodiment 3. As shown in FIG. 10, delay line 18 can beprovided between transistor Tr11 and capacitor 21. Terminal device 130and terminal device 120 are identical in all their configurations otherthan a difference in positions of delay line 18.

The voltage from power generator circuit 10 is supplied to determinatorcircuit 13 according to Embodiment 3not via control circuit 12. In otherwords, a part of the electric power provided by power generator circuit10 is supplied to determinator circuit 13 directly rather than viacontrol circuit 12. An output of determinator circuit 13 can be read atthe input port of control circuit 12 similarly to Embodiment 1.

3-2. Operation of Terminal Device for Registration

FIG. 11 is a timing chart when terminal device 120 shifts operation to aregistration mode.

Power generator circuit 10 generates electric power Vbat whenever window52 is opened or closed. Voltage converter 11 disregards a low voltagenot higher than of 1.85V by the UVLO function, so that power-supplyvoltage VDD can be a pulse shape shown in FIG. 11. Output impedance ofvoltage detector 17 becomes high at voltages higher than 1.85V and nothigher than 1.85V. Transistor Tr11 is turned off (OFF) when the outputimpedance of voltage detector 17 becomes high. Transistor Tr11 is turnedon (ON) when the output impedance becomes low. When transistor Tr11 isturned on, a voltage is supplied to determinator circuit 13. Thisvoltage decreases according to time constant τ, and the voltage is readat the input port.

Control circuit 12 reads the output of determinator circuit 13 when awaveform of power-supply voltage VDD rises, similarly to control circuit12 according to Embodiment 1. Control circuit 12 then outputs digit “1”when a voltage value read is not lower than a predetermined high level(H). On the other hand, control circuit 12 outputs digit “0” when thevoltage value read is not higher than a predetermined low level (L).Subsequently, control circuit 12 switches the operating mode to aregistration mode when an output pattern for plural times coincides witha predetermined output pattern. As described, control circuit 12 ofterminal device 120, after it starts up, shifts from the normal mode tothe registration mode based on the plural startup timings.

3-3. Beneficial Effects

According to Embodiment 3, the electric charge conventionallydisregarded can be supplied to determinator circuit 13, and the energycan be used efficiently. Hence, the electric power can be suppliedsufficiently to control circuit 12 and transmitter circuit 14.

In addition, delay line 18 can stabilize an output value of determinatorcircuit 13, and control circuit 12 reads the output of determinatorcircuit 13 accurately.

Description of configurations similar to those of the first embodimentand their effects is skipped.

INDUSTRIAL APPLICABILITY

The terminal devices according to Embodiments 1 to 3 are capable ofshifting operating mode to a registration mode using the same operationand mechanism as the normal mode. The terminal devices are thereforeapplicable to wireless communication systems, such as so-calledenergy-harvesting wireless communication.

REFERENCE MARKS IN THE DRAWINGS

-   100, 110, 120, 130 terminal device-   300, 310 master wireless device-   50 window frame-   51 user-   52 window-   10 power generator circuit-   11 voltage converter-   12 control circuit-   121 non-volatile memory-   122 central processing unit-   13 determinator circuit-   14 transmitter circuit-   15 antenna-   16 receiver circuit-   17 voltage detector-   30 receiver circuit-   31 antenna-   32 control circuit-   321 non-volatile memory-   322 central processing unit-   33 power supply-   34 transmitter circuit

1. A terminal device capable of communicating with a master wirelessdevice, the terminal device comprising a control circuit, wherein thecontrol circuit has operating modes including a normal mode foroutputting startup information relating to startup of the terminaldevice, and a registration mode for outputting registration informationrelating to registration of the terminal device with the master wirelessdevice, and wherein the control circuit shifts one of the operatingmodes to the registration mode based on timing of a plurality ofstartups of the terminal device.
 2. The terminal device according toclaim 1, further comprising a determinator circuit that determineswhether or not a predetermined time elapses from a preceding startup toa next startup of the terminal device.
 3. The terminal device accordingto claim 2, wherein the terminal device determines the timing using anoutput of the determinator circuit.
 4. The terminal device according toclaim 3, further comprising a power generator circuit, wherein a part ofelectric power provided by the power generator circuit is supplied tothe determinator circuit not via the control circuit.
 5. The terminaldevice according to claim 1, further comprising a power generatorcircuit, wherein the terminal device transmits the startup informationand the registration information to the master wireless device usingelectric power provided by the power generator circuit.
 6. A wirelesscommunication system comprising a master wireless device and a terminaldevice capable of communicating with the master wireless device, whereinthe terminal device includes a control circuit, wherein the controlcircuit has operating modes including a normal mode for outputtingstartup information relating to startup of the terminal device, and aregistration mode for outputting registration information relating toregistration of the terminal device with the master wireless device,wherein the control circuit shifts one of the operating modes to theregistration mode based on timing of a plurality of startups of theterminal device, and wherein the registration information is transmittedto the master wireless device from the terminal device, and received bythe master wireless device as to resister the terminal device with themaster wireless device.
 7. The wireless communication system accordingto claim 6, wherein, upon receiving the registration information, themaster wireless device transmits an encryption key to the terminaldevice, and wherein the terminal device receives and stores theencryption key.
 8. The wireless communication system according to claim7, wherein the encryption key transmitted from the master wirelessdevice to the terminal device is different from another encryption keypreviously transmitted from the master wireless device.
 9. The wirelesscommunication system according to claim 7, wherein transmission power ofthe master wireless device for transmitting the encryption key is largerthan transmission power of the terminal device for transmitting theregistration information.